The introduction of touch panels into avionics has significantly reduced pilot workload and simplified user interfaces. Application of touch panels into the cockpit environment presents unique challenges related to both the environment and use cases. There are two common types of touch panels, resistive and capacitive. Resistive touch panels are robust but lack a few key characteristics of capacitive touch panels, namely: increased activation forces and decreased ability to support multi-touch activations. When applying a resistive touch panel in a cockpit environment, it is often necessary to add a mechanical protective cover. The addition of this cover will increase activation forces, which can cause difficult operation, especially for drag or swipe touch gestures. In addition, resistive touch panels have limited support for multi-touch operations without significantly increased complexity and cost.
Capacitive touch panels may offer reduced activation force and simpler support for multi-touch gestures. However, when applied in a cockpit environment, such capacitive touch panels may be susceptible to electromagnetic interference (EMI). EMI can originate from natural (lightning) or man-made (radio transmitter) sources. The interaction of EMI and a capacitive touch panel may cause a failure mode that can create significant safety issues. If a capacitive touch panel is exposed to certain electromagnetic fields then the touch panel can register an event with no pilot actuation. If this occurs without a pilot detecting it then the avionics under control of the capacitive touch panel could place the aircraft into an unsafe condition.